This invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a technology to improve moisture resistance of a semiconductor device.
In semiconductor devices, aluminum wiring is frequently used at present. However, aluminum wiring is apt to become extremely corroded. Such wiring corrosion is simply called corrosion, and is a the very serious problem from a viewpoint of reliability of the semiconductor integrated circuit device. One of the causes of corrosion of aluminum wiring is moisture. By incursion of moisture, the moisture resistance of the semiconductor device is deteriorated. Particularly, in so called plastic packages molded by plastic resin, adhesion between the plastic resin and metal such as copper serving as a lead is poor. As a result, it is difficult to completely prevent moisture diffusion from the lead portion on the package side surface. Further, the plastic resin itself is somewhat has hygroscopic property.
For this reason, as a measure for improving moisture resistance of the semiconductor chip, passivation film (surface protective film) is conventionally used. For such a passivation film, a layered product comprised of a silicon nitride film (Si.sub.3 N.sub.4), or Si.sub.3 N.sub.4 /PSG film, etc. is used. This passivation film can advantageously protect moisture incursion from the upper direction of the semiconductor chip . Meanwhile, in the process for manufacturing semiconductor devices, after a passivation film is formed on the entire surface of the wafer, the wafer is subjected to dicing. Thus, chips are quarried. In this case, however, since the side surface of the chip having a cutting plane is not covered by the passivation film, incursion of moisture from the chip side surface constitutes a great problem. Namely, moisture comes into contact with BPSG film or PSG used as an insulating film to produce phosphoric acid. This phosphoric acid corrodes aluminum wiring, etc.
As stated above, the conventional semiconductor devices have the problem that aluminum wirings and/or elements in the chip would be corroded by incursion of moisture from the side surface where there is a cutting plane of a semiconductor chip formed by dicing a semiconductor wafer, disadvantageously resulting in an unsatisfactory operation.